Method of making a commutator



Jan. 30, 1940. ANDREWS 2,188,423

METHOD OF MAKING A COMMUTATOR Filed July 9, 1958 XNVENTOR ATTO R N EYSPatented Jan. 30, 1940 UNITED STATES PATENT OFFICE 2 Claims.

This invention relates to new and useful improvements in commutators andmethod of making the same, and more particularly to commutators of thesmaller sizes such as are used on small motors.

An object of the invention is to provide an inexpensive construction ofcommutator wherein the metal conducting segments are securely held by aninsulating hub.

Another object is to provide a simple and inexpensive method of makingsaid commutators.

Other objects and advantages will become apparent from a considerationof the following de' tailed description taken in connection with the theaccompanying drawing wherein a satisfactory embodiment of the inventionis shown. However, it is to be understood that the invention is notlimited to the details disclosed but includes all such variations andmodifications as fall within the scope of the invention and of theappended claims.

In the drawing:

Fig. 1 is a side elevational view showing a tube of conducting materialfrom which the segments of the commutators of the invention are to bemade;

Fig, 2 is an end view of such tube;

Fig. 3 is an enlarged end view of a section of the tube cut to thelength desired for the commutator to be made;

Fig. 4 is a sectional view as along the line 4-4 of Fig. 3;

Fig. 5 is a view similar to Fig. 3 but with the insulating hub moldedinto the tube section;

35 Fig. 6 is a sectional view taken as along the line 66 of Fig. 5;

Fig. '7 is an end view of the finished commutator; and

Fig. 8 is a side elevational view of the commutator of Fig. 7.

Referring in detail to the drawing, the completed commutator is shown inFigs. '7 and 8 wherein it is generally designated Ill. The first step inmaking up the commutator i0 is the providing of a tube I i of anysuitable metal, such for example as copper or copper alloy, which may beof any desired length and which is made by extruding, drawing, or thelike. On its inner surface tube H is provided with a series of longi-,

tudinally extending spaced ribs l2 extending for the length of andformed integral with the tube.

Next a section of the tube of the desired length, and which section ishereinafter designated I3, is cut from the tube ll. Either before orafter section I3 is cut from the tube II the ribs on the inner surfaceof said section are cut away intermediate their ends as indicated at 9whereby in the section the ribs provide spaced lugs l4 located adjacentthe ends of the section.

In cutting away the intermediate portions of the ribs to provide thelugs I4 the metal is removed in such a manner that the inner opposingends of the lugs are undercut as shown at l5 whereby such ends l5comprise oppositely inclined surfaces each inclining toward the outersurface of the section. Thus with each two aligned lugs l4 beingconsidered a pair it will be apparent that the spaces 9 between theopposing ends of the lugs of each pair are dovetailed.

A center or hub I6 of insulating material is then molded into thesection l3 providing the construction shown in Figs. 5 and 6, thisinsulating material preferably filling the space within the section. HubHi has a shaft opening I! therethrough and it is noted that the materialof the hub has entered into the spaces l8 (see Fig. 3) between thelaterally adjacent lugs l4 whereby to provide portions or ribs H! (seeFig. 5). By reference to Fig. 6 it will be noted that there are dovetailshaped portions 20 of the molded hub I 6 located in the spaces betweenthe inclined end surfaces l 5 of the lugs l4. Thus it will be apparentthat the hub l6 and the tube section l3 are mechanically connected orlocked together.

A convenient method of molding the insulating center or hub portion ISin the section I3 is to insert the section in an opening in a die and ofa diameter equal to that of the section, with means to hold a pin of theproper size at the center of the section. Then the proper amount of themoldable material, such for example as Bakelite or similar material isplaced in the section about the pin and compressed by a plunger betweenheated platens or plates. After the molded material has hardened or setthe section is removed from the die, and after the parts have cooled thepin can be easily slid out leaving the opening I l for mounting thecommutator on a shaft or other support.

To complete the commutator the section I3 is now out longitudinally asshown at 2| at each side of each pair of aligned lugs l4. Slots 2| arethus provided dividing the metal tube section into a plurality ofcommutator segments 22 (see Figs. 7 and 8) separated laterally from oneanother by said slots. Each segment 22 includes a pair of the lugs I 4embedded in the molded insulating hub l 6 so as to have portions of thelug locked to the hub as some of the material of the latter has formedthe dovetail interlocks 20 with such lugs.

Each segment 22 may be provided with a short slot or notch 23 to be usedin connecting the necessary lead wires to the segments. As the lugs orrib sections I4 are at the ends of the commutator they provide plenty ofstock for these slots or notches 23.

From the foregoing it will be seen that the commutator of the inventionmay be inexpensively made and that yet the article is of sturdyconstruction, the individual conductor segments being each securelylocked to the insulating hub. The ribs l2 are formed in the tube I I asthe latter is formed and then insofar as the conductor portions of thecommutator are concerned the only further treatment required is that theribs be cut to provide the undercut ends [5 and that finally the tube becut or slotted to separate the segments 2i from one another. The lugs [4securely lock the segments to the hub l6 as the integral dovetailed hubportions 20 overlie the lugs in such manner that the latter cannot pulloutof the hub. These portions 20 also effectively hold the segmentsagainst sliding movements longitudinally of the commutator.

Having thus set forth the nature of my invention, what I claim is:

l. The method of making a commutator comprising providing a shorttubular element of wrought conducting material having circumferentiallyspaced longitudinal ribs of substantially uniform thickness on its innersurface integral therewith along their outer longitudinal edges,

cutting each of said ribs transversely intermediate its ends to provideit with a pair of spaced opposed surface portions inclined in cppositedirections so they are spaced farther at their outer than their inneredges, molding a hub of insulating material into said tubular elementwith portions of the hub entering and filling the spaces between theopposed surfaces of said ribs, and then slitting said elementlongitudinally between said ribs to divide the element into a pluralityof spaced segments.

2. The method of making a commutator comprising forming a tube ofwrought conducting material having circumferentially spacedlongitudinally extending ribs on its inner surface integral therewithalong their longitudinal edges, the side walls of said ribs extendingsubstantially radially of thetube so that the ribs are ofsubstantiallyuniform thickness, severing from said tube a .sectionthereof equal to the length of the commutator segment desired, removingportions of said ribs intermediate their ends in a manner to provideeach rib with opposed undercut end surface portions, molding a hub ofinsulating material into said tube section with portions of the hubentering and filling the spaces between the opposed undercut surfaceportions of the ribs, and then slitting said tube sectionlongitudinallybetween said ribs to divide the section into a pluralityof spaced segments.

GEORGE E. ANDREWS.

